Electrical interconnect techniques typically require electrical connection between metal or other conductive layers, or regions, which are present at different elevations within or overlying a semiconductor substrate. Such interconnecting typically is conducted, in part, by etching a trench and/or a contact opening through insulating material to a lower elevation metal layer or metallized region. For example, contact openings commonly are fabricated to make conductive contact to a metal silicide region of a metal-oxide-semiconductor field effect transistor (MOSFET). Trenches and contact openings also are conventionally fabricated to various metal layers to ultimately connect one semiconductor device element on one elevation to another semiconductor device element on another elevation.
Typically, as part of the process for fabricating a contact opening, a photoresist layer is deposited on the insulating material. The photoresist is patterned and etched to expose portions of the insulating layer and transfer the pattern to the insulating layer. The insulating layer is etched to the lower metal layer or region (hereinafter referred to collectively as “metal region”), forming a contact opening within the insulating layer to the metal region. The photoresist then is stripped from the insulating layer and a conductive material is deposited within the contact opening.
During the etching of the contact opening and the subsequent stripping of the photoresist, however, etching residue such as polymer from the photoresist can settle onto the exposed lower metal region. In addition, the metal region can be oxidized by exposure to oxygen in the environment. Some small resistance is associated with each contact between a conductor formed within the contact opening and a metal region. However, etching residue and metal oxide on the metal region increase that resistance, thereby decreasing device performance. Various methods have been used and suggested for cleaning the metal region after formation of the contact opening and before deposition of the conductive material within the contact opening. For example, ionized argon typically has been used to clean the metal region. However, ionized argon can result in sputtering of the metal region. Oxygen-based plasma also has been used, but oxygen-based plasma results in oxidation of the metal region. To reduce contact resistance and enhance device performance, the semiconductor industry is transitioning from cobalt silicide (CoSi2) to nickel silicide (NiSi) for MOSFET contacts. However, NiSi is quickly oxidized by oxygen plasma to form nickel oxide, which greatly increases the resistivity of the contact. The use of hydrogen-containing plasma has been suggested to clean the metal region. However, the use of hydrogen-containing plasma can be slower and less efficient than desired.
Accordingly, it is desirable to provide improved methods for stripping photoresist and/or cleaning metal regions of semiconductor structures. It is also desirable to provide stripping and/or cleaning methods that do not result in sputtering or oxidation of the metal regions. In addition, it is desirable to provide methods for stripping photoresist and/or cleaning metal regions at enhanced stripping and cleaning rates. It also is desirable to provide methods for fabricating semiconductor structures utilizing such stripping and cleaning methods. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.